1. Field of the Invention
The present invention relates to a metal complex assembly and production thereof, which metal complex assembly is suitable for constituting nanoscale devices capable of operating at ultrahigh density and ultrahigh speed, such as molecular devices, matrix circuits, molecular functional devices and logical circuits and is applicable to the miniaturization and elaboration of devices and apparatus in information and communication fields, such as arithmetic and logic units, displays and memories. The present invention also relates to a multidentate ligand that is suitable for the metal complex assembly, and to a polynuclear metal complex and a metal complex chain using the multidentate ligand.
2. Description of the Related Art
Electronic circuits using semiconductor devices serve as the backbone of technologies typically in information and communication fields and computer fields. To increase the throughput of such semiconductor devices, investigations have been made to reduce the line width of traces to be printed on a substrate and to increase a packing density of the circuit.
However, such techniques for size reduction have their limits due to quantum-theoretical influence. Thus, investigations have been made on, as a completely novel technology, molecular devices comprising a molecule or molecular assembly that works as a device.
Certain proposals have been made on driving principles and models of the molecular devices.
Batlogg et al. found that an organic crystal exhibits conductive or superconductive property by applying a technology on field-effect transistors (FET) (refer to J. H. Schon, Ch. Kolc, B. Batlogg, Nature, 406, 702 (2000)). This property is also found in fullerenes and metal complexes, is suspected to impart a switching function to various compound molecules by the action of carrier doping upon application of an electric field and receives attention.
Wada et al. proposed a model of molecular single-electron transistor comprising fullerenes as quantum dots as a candidate for single-molecular devices (refer to Japanese Patent Application Laid-Open (JP-A) No. 11-266007). According to this technology, electrodes are in tunnel junction with the quantum dot, the potential of the quantum dot is changed by the action of a voltage of a gate arranged through an insulative phase to thereby exhibit functions as a transistor.
Attempts have been made to apply a supramolecule having various structural and functional properties to switching by utilizing its molecular recognition function. The supermolecule comprises an organized assembly of plural molecules by the action of a non-covalent interaction such as coordinate bonding, hydrogen bonding and/or intermolecular force and thereby has various structural and functional properties which respective molecules alone cannot have. Balzani et al. proposed a molecular switch that changes its behavior by the action of an external field such as pH or light, using a supermolecular compound having a molecular recognition function, such as a catenane or rotaxane (refer to V. Balzani, A. Credi, and M. Venturi, Coord. Chem. Rev., 171, 3 (1998)).
Regarding wiring technologies in such molecular devices, an attempt has been made to provide wiring and connecting by introducing a functional group such as thiol group to a terminal of a conductive macromolecule and forming wiring of, for example, gold or ITO electrode utilizing chemical adsorption of the functional group with respect to the gold or ITO electrode.
As is described above, various investigations have been made on the molecular devices. However, technologies that provide practical molecular devices or circuits using the same have not yet been provided.
To design and construct the molecular device or a circuit using the same, the arrangement or array of individual molecules, recognition of individual molecules, access to individual molecules, and wiring and addressing for closely connecting between specific molecular devices to form a circuit must be carried out properly. For example, regarding the arrangement or array of individual molecules, a technique of arranging atoms one by one using a scanning probe microscope (SPM) is developing, but it is not realistic as a technique for designing or constructing nanoscale devices. Regarding the wiring, it is considered to be practical to drive the molecular devices by electron signals in a solid as in semiconductor devices. However, a macroscale conductor cannot be significantly connected to such a molecular-level device.
Molecular wires comprising a single chain macromolecule or an assembly of one-dimensionally assembled molecules may serve as an electroconductive path or a switch in the molecular devices and are believed to be a key element in the design or construction of the molecular devices or circuits using the same.
However, the electroconductive mechanisms of molecular wires are currently under study and have not yet been clarified sufficiently. In addition, such simple one-dimensional substances lose their electric conductivity due to specific properties in one-dimensional substances, such as Peierls transition, and are difficult to form into molecular wires.
Metal complex chains, especially ladder complexes are promising candidates for the molecular wire, and properties thereof have been theoretically studied initially by Rice et al. A ladder structure called as a spin ladder comprising an even number of aligned antiferromagnetic metal chains is expected to be superconductive by doping a carrier (refer to T. M. Rice, S. Gopalan and M. Sigrist, Europhys. Lett., 23 445 (1993)), and there is possibility that it functions as a device. As an experimental example, a two-leg ladder compound using a copper oxide was synthesized and was found to be superconductive under high pressure (refer to M. Uehara, T. Nagata, J. Akimitsu, H. Takahashi, H. Mori and K. Kinoshita, J. Phys. Soc. Jpn, 65, 2764 (1996)). Kimizuka et al. have investigated on the formation of the molecular wire by dispersing a halogen-bridged metal complex coated with an organic counter anion (refer to N. Kimizuka, N. Oda, T. Kunitake, Inorg. Chem. 39, 2684 (2000)). A ladder compound using a metal complex composed of p-EPYNN and Ni(dmit)2 has also been studied (refer to H. Imai, T. Inabe, T. Otsuka, T. Okuno, and K. Awaga, Phis. Rev. B 54, R6838 (1996)). In addition, “crossbar switches” have been increasingly investigated as a possible candidate for a nanodevice which does not require complex processing (e.g., James R. Heath, Philip J. Kuekes, Gregory S. Snider, R. Stanley Williams, Science Vol. 280 (1998)). In the crossbar switches, the switching at the intersection point between nanowires (nanoscale wire) crossing each other is controlled by an input from the nanowires. Thus, if an array of the nanowires is constituted on the molecular level and in a bottom-up manner, ultradense devices can be relatively easily provided.
However, these are only expectations or experimental estimations and lack practicality and specificity. These cannot be significantly achieved by conventional technologies, and demands have been made on a novel technique that can realize, for example, the molecular-level wiring on the molecular level in a bottom-up manner. Certain metal complex assemblies have been synthetically prepared (refer to W. Huang, S. Gou, D. Hu, S. Chantrapromma, H. Fun, and Q.
Meng, Inorg. Chem., 40, 1712 (2001)). However, in most cases, molecules are arrayed as a ladder only by the action of a weak interaction such as intermolecular force, and it is difficult to control to pack such molecules. The molecular array of the resulting metal complex chain significantly depends on the molecular form, effects of substituents, subtle interactions between molecules and other factors and may not possibly become a ladder structure even if chemically modified. Thus, the metal complex chain cannot sufficiently serve as a single wire.